A large spectrum of medicinal properties has been ascribed to garlic (Allium Sativum L.), which makes it one of the most popular medicinal herbs. Garlic preparations have been used from ancient times in folk medicine of different countries for a variety of disorders. Recently, there has been a resumption of interest in the therapeutic properties of garlic, and garlic has become the subject of an increasing number of biochemical and clinical studies.
Most of the active ingredients in crushed garlic are sulfur-containing compounds. The major component was identified as allicin (thio-2-propene-1-sulfinic acid S-allyl ester). The intact garlic clove does not contain allicin, but rather contains its odorless precursor alliin (S-allyl-L-cysteine sulfoxide). In garlic cloves, an enzyme (C-S-lyase, known as alliin lyase or alliinase [E.C. 4.4.1.4]) is present that converts alliin to allicin, pyruvate, and ammonia. Alliin and alliinase are found in different compartments of the garlic cloves. When garlic is cut or crushed, the membranes of these compartments are broken so that the enzyme can react with its precursor, alliin.
Allicin is a chemically unstable colorless liquid that it believed to be responsible for both the odor and much of the biological activity ascribed to garlic. Thus, allicin possesses a remarkably broad spectrum of antibiotic activities, including antibacterial activity against a wide range of Gram-negative and Gram-positive aerobic and anaerobic bacteria, as well as antifungal, antiprotozoal, antiviral, antiparasitic, and insecticidal activities. Miron et al (international publicaton WO 97/39115) discloses a biotechnological process for preparing pure allicin in practically unlimited amounts.
Many recent studies have reported the beneficial effects of allicin on cardiovascular risk factors, particularly serum cholesterol and triglyceride levels as well as lipoprotein balance, hypertonia, and thrombogenesis in animals and in humans. These studies consistently demonstrate that allicin can induce an increase in fibrinolytic activity (Bordia et al, 1997; Kieswetter, 1990), inhibit platelet aggregation (Makheja and Bayley, 1990), improve lipid profile including reducing serum cholesterol levels, decreasing blood pressure, and preventing formation of strokes (Augusti and Mathew, 1974; Bordia et al, 1975; Bordia and Verma, 1980; Knipschid and ter-Riet, 1989; Eilat et al, 1995; Abramovitz et al, 1998). The present inventors have also found that allicin has pronounced anticancer potential.
Most of the beneficial and versatile activities of allicin were experimentally demonstrated in vitro. Allicin is a very chemically active molecule, which readily reacts with compounds in the body and disappears within a few minutes after being mixed with blood. In vivo activities of allicin can be defined as unique activities, that is, those exhibited only by allicin itself, and non-unique activities, those which are exhibited by allicin derivatives or secondary products produced from allicin during treatment with allicin. For example, the most valuable intrinsic activity of allicin is its prominent and broad spectrum antibiotic activity. However, this activity has been noted only for allicin and one of its derivatives, ajoene. The activity of allicin against several microorganisms is very important, especially in cases in which effective therapy has still not yet been developed. The cytotoxic properties of allicin are significantly higher than those of other sulfur compounds derived from garlic, and the present inventors have demonstrated that purified allicin was effective against cancer cells in concentrations significantly lower than those effective to kill normal cells (Hirsh et al, 2000).
One of the problems with using allicin as a drug to treat cancer or infectious diseases is that the allicin molecule is very reactive and rapidly becomes inactivated upon reaction with SH-proteins and non-protein thiols. Therefore, it would be highly desirable to provide allicin in a form such that it could exert its beneficial biological properties, including antibacterial and antitumor activities, at the desired site of the body.